Lapping compositions for polishing, sharpening and otherwise treating metal surfaces have heretofore been known. In general, the lapping compositions include an inorganic grit type material that serves as an abrasive, and that is suspended in a particular medium. The composition is applied with force against a particular surface to be polished, ground or the like.
Two types of lapping compounds or compositions really exist, being divided between polishing and grinding compounds. In a polishing composition, the grit is, of course, much smaller, is held in a particular type suspension, and is applied against a metal to be polished to obtain a smooth surface without residual scratches or other disfigurements. In a grinding composition, the grit is substantially larger, and is designed to abrade away a larger portion of a material without the necessity of obtaining an ultimate finely smooth, polished surface.
The present invention is directed primarily to a composition for use in sharpening or grinding cutting elements as opposed to polishing to a shine, though the composition of the present invention in particular embodiments may be employed for polishing application. Reel type lawnmowers for cutting industrial lawns, golf fairways, greens, tees, etc., athletic fields, parks and the like are set forth by way of example. For simplicity purposes, all further discussion is directed to a reel type mower, though as mentioned herein, numerous other cutting elements may likewise be sharpened by the present lapping composition. Very even cutting edges are necessary if the golf greens, for example, are to be properly cut. Extreme care must thus be taken to avoid uneven edges on the reel type mowers which will dish out the greens during cutting and leave uneven surfaces for putting. Generally speaking, the lapping compounds for reel type mowers have historically been oil base compositions, or liquid detergent base compositions.
Problems have existed with prior art lapping compositions. A general inability to retain the grit in suspension has been evident. Prior art compositions have experienced settling of the grit to the bottom of the medium. Thereafter, extreme difficulty is encountered for adequate remixing to the point of obtaining a good suspension. It is thus very difficult to obtain a uniformly sharp edge with prior art compositions since a permanent suspension is really needed to accomplish same. Furthermore, during sharpening of the lawnmower reels, which are normally driven backward by an external drive means at a speed of about 100 revolutions per minute, the grit of the prior art compositions has been slung off the reel by centrifugal force. As such, excess lapping composition has been required to replace that lost during lapping. Also, the possibility of uneven sharpening due to failure to maintain a proper level of lapping composition on the reel is always present.
Another problem that exists with prior compositions is removal of the composition from the reel after sharpening. Once the reel has been sharpened, it is absolutely necessary that all the grit be removed from the blades. Should any grit remain on the reel, continued grinding will occur during rotation of the reel. A dished out section will be produced on the blade very quickly which alters even cutting of the desired turf surface. With oil base systems, an organic solvent must first be applied onto the reel to cut the oil after which the reel must be washed. Furthermore, with a liquid detergent system, which usually contains sodium carboxy methylcellulose as a primary thickener, a permanent suspension is not found and also difficulty is experienced in complete cleaning of the reel as well as keeping the grit from walking off the reel during lapping.
The prior art does not teach or suggest the present invention. Exemplary of the prior art are U.S. Pat. No. 2,375,823 to Saunders et al; U.S. Pat. No. 2,783,137 to Roth; U.S. Pat. No. 2,944,879 to Allen et al; U.S. Pat. No. 2,944,880 to Allen et al; U.S. Pat. No. 2,980,524 to Morton; U.S. Pat. No. 3,020,140 to Bluth et al; U.S. Pat. No. 3,170,273 to Walsh et al; U.S. Pat. No. 3,663,475 to Figiel; U.S. Pat. No. 3,715,842 to Tredinnick et al; U.S. Pat. No. 3,779,727 to Siqui et al; U.S. Pat. No. 3,804,607 to Jungell, and U.S. Pat. No. 3,817,727 to Yancey.